Phospholipide metabolism in cell fractions of regenerating liver

The P³² uptake in a number of phosphorus-containing fractions of the nuclei, mitochondria, microsomes, and supernatant of liver cells was investigated in normal rat liver and during the premitotic and mitotic phases of liver “regeneration” following partial hepatectomy. The cephalins of all the cell fractions of the normal livers incorporated P³² much faster than the lecithins, while the sphingomyelins incorporated it relatively slowly. The increased P32 uptake of the phospholipides observed earlier to be associated with mitotic activity can be accounted for by an increased P³² uptake by the cephalins of the nucleus, by the lecithins of the mitochondria, microsomes, supernatant, and possibly the nuclei, and by the sphingomyelins of the supernatant. The data, viewed in the light of observations made in earlier studies, suggest that P³² turnover in lecithin occurs in all parts of the cell during interphase; that of nuclear cephalins and of supernatant sphingomyelins occurs following preprophase and prior to or during metaphase processes.